Segment for rotary abrasive devices



Sept. 11, 1962 A. BLOCK SEGMENT FOR ROTARY ABRASIVE DEVICES Filed Aug. 1, 1960 Unite '1! States Patet 3,053,021 SEGMENT FOR RGTARY ABRASIVE DEVICES Aleck Block, 3691 Lewanee Ave., Los Angeles, Calif. Filed Aug. 1, 1960, Ser. No. 46,757 16 Claims. (Cl. 51193.5)

This invention relates to rotary abrasive devices utilizing replaceable and discardable abrasive segments comprising packs of abrasive sheets having root portions secured together and provided with means for detachable anchorage thereof to a rotatable hub or the like. The general object of this invention is to provide an improved means for securing the root portions of the abrasive leaves together and an improved means for demountably anchoring the root section of an abrasive pack to a rotary hub device.

Another object is to provide an improved, simplified and less expensive method of fabricating an abrasive pack with a demountable root section.

A further object is to provide an improved rotary abrasive device embodying detachable abrasive packs.

In general, the invention provides an abrasive pack composed of a plurality of abrasive-coated leaves and spacers of compressible sheet material interposed between at least the root portions of the leaves, in alternating array, and provided with a-root section having a relatively thin waist portion and a thicker butt portion adapted to be keyed into a retainer channel or slot in a rotary hub, the root portions being adhesively secured together and the waist portion being thinned by compression while the adhesive is being cured or otherwise set.

Other objects and advantages will become apparent in the ensuing specifications and appended drawings in which:

FIG. 1 is a perspective view of an assembly of abrasive leaves in an early stage of fabrication of an abrasive pack therefrom;

FIG. 2 illustrates a subsequent step in fabricating the abrasive pack;

FIG. 3 illustrates an alternative for the step shown in FIG. 2;

FIG. 4 illustrates a subsequent step in the fabrication of the abrasive pack;

FIG. 5 illustrates the finished abrasive pack and its mounting in an anchor socket of an abrasive drum;

FIG. 6 shows a modified form of abrasive segment and a modified form of the method of fabricating;

FIG. 7 illustrates a modified type of rotary abrasive device utilizing the abrasive pack of my invention;

FIG. 8 shows a further modified form of my improved abrasive segment; and

FIG. 9 is a fragmentary enlarged sectional view of another modified form of the invention.

Description of Preferred Form-FIG. 5

Referring now to the drawings in detail, I have shown in FIG. 5 thereof, as an example of one form in which the invention may be embodied, a rotary abrasive device comprising the improved abrasive pack of my invention, indicated at A, and a rotary abrasive drum B having a dovetail socket 10 in which the root section 11 of the abrasive pack A is demountably anchored.

The abrasive pack A comprises a plurality of sheets 12 of strong paper or cloth each coated on one side thereof with a coating of abrasive grit 13, the abrasive coatings all facing in a common direction. The abrasive coated sheets have root portions which are bonded together to provide a common root section 14 for the entire pack, the remainder of the abrasive sheets, comprising the major area thereof, consisting in a plurality of freely flexible working portions 15 secured together by the common root section 14 but otherwise free of attachment to one another and thus free to flex upon contact with a work surface.

The root section 14 is composed of the root portions of the sheets 12 and a series of spacer strips 16 of compressible sheet material intervening between successive pairs of the sheets 12, the root portions of the abrasive sheets being firmly bonded to the spacer strips 16 by a suitable adhesive such as epoxy resin or any other resin or glue of sufficiently high tenacity and resistance to moisture. Spacer strips 16 may be of thick paper or cardboard or of any other material having equivalent compressibility and ability to absorb the adhesive.

The root section 14 of the pack has a waist area of minimum width defined between a pair of V-grooves 17 in the opposite faces of the root section 14, extending in spaced parallel relation to the inner end of the abrasive pack. The spacer strips 16 are compressed and progressively thinned toward the waist area of root section 14 as defined between the bottoms of the grooves 17, the thinned areas being of increased density as contrasted to the marginal areas of the spacer strips, which are of maximum thickness. The abrasive grains of the root portions of the respective abrasive sheets 12 are embedded in the adjoining surfaces of the spacer strips 16 so as to contribute to the reduction in thickness of the root section 14 in the waist area thereof, and so as to have high high density and rigidity in the center of root section 14, where bending forces imparted thereto by leaves 12 and intensified by leverage action, are of high intensity.

The butt portion 18 of the root section 14 is of wedge shape, proportioned to fit snugly in the dove-tail socket 10 of the rotary hub B, and may be inserted therein by sliding the pack into one end of the socket 10, parallel to the axis of rotation of the hub B.

The root section 14 is thoroughly impregnated with the resin or adhesive by which the abrasive sheets are bonded to the spacer strips 16. The spacer strips 16 may be of paper of sufficient porosity to permit the liquid resin or other adhesive to penetrate the same in the fabrication of the abrasive pack, so that after the resin or other adhesive has cured or dried or otherwise hardened, the root section 14 will become quite rigid, solid, hard and incompressible. Accordingly, the butt portion 18 thereof will function to securely anchor the abrasive pack in the socket 10, resisting radially outward escape from the hub B when being rotated at high speed with the abrasive leaves 12 forcibly striking a work surface.

The spacer strips 16 serve to maintain the abrasive leaves 12 in spaced relation to one another as best shown in FIG. 4, thus providing substantially increased flexibility over that which would be obtained in a pack of abrasive sheets in direct face to back contact with one another (wherein such contact would tend to inhibit the free move-' ment of the abrasive leaves relative to one another). The strips 16, which are more compressible than abrasive sheets 12, have the further function of yielding to the compressive forces applied by jaws 24c and becoming suificiently thinned in their central areas to develop the double dovetail cross section of root section 14.

Method 0 Fabrication FIG. 1 illustrates a preliminary step in which the spacer strips 16 have'been interleaved between a plurality of the abrasive coated sheets 12, prior to adhesivelysecuring the spacer strips between the abrasive sheets.

FIG. 2 illustrates a subsequent step of impregnating th root portions of the abrasive sheets and the intervening spacer strips 16 by dipping the root section of the FIG. 1 assembly into a body of adhesive 20 contained in a suitable container 21. The adhesive body 20 is in relatively thin liquid form for maximum penetrating qualities,

3 which may be improved by the addition of a suitable wetting agent.

FIG. 3 illustrates an alternative method of impregnating the root area of the assembly of abrasive leaves and spacer strips 16, wherein the assembly is inverted, with the spacer strips 16 at the top and adhesive 20a is brushed or poured onto the aligned edges of the abrasive sheets and spacer strips at the upper end of the inverted assembly, and permitted to seep downwardly into the sandwich structure of spacer strips and abrasive sheets. While the adhesive is shown as being applied by a brush 22, it will be understood that it may be ejected from a nozzle, or poured from a pouring spout of a suitable container.

FIG. 4 illustrates a subsequent step in the processing of the assembly of abrasive leaves and spacers after the root portions thereof have been thoroughly impregnated with resin or other adhesive. Pressure is applied to the root portions of the abrasive sheets by a pair of jaws 24 having V-noses 25 of blunt wedge form such as to impart the desired V-groove cross section to the root section 14 of the pack. The jaws 24 are brought together against the root areas of the assembly, under high pressure which crushes the root portions of the abrasive leaves into the intervening spacer strips 16 and thins down and densities the medial areas of the spacer strips 16. The porous fibrous (eg. matted or felted) structure of the strips 16 is such as to be subject to thinning and compacting the same when subjected to the high pressure, and thus the cross sectional thickness of the sandwich structure of the assembly is suitably reduced across the waist area of the root section 14 as the pressure is applied. The pressure of jaws 24 is maintained while the impregnated root section 14 is subjected to heat or other curing step such as to harden the resin or other adhesive into a rigid, hard, dense matrix impregnating and filling the spacer strips 16, the sheets 12, and the spaces between the abrasive grains 13 so that the root section 14, when cured or otherwise hardened, is strong, dense, hard and substantially incompressi-ble.

The curing of the resin secures the spacer strips 16 and the root portions of sheets 12 in the compressed and thinned condition imparted thereto by the jaws 24, preventing any expansion of the root section 14 when the pressure of the jaws is relieved.

The completed abrasive pack as shown in FIG. 5, may subsequently be slipped into a hub socket and secured by suitable end flanges or caps (not shown) so as to prepare the abrasive drum for high speed rotary abrasive operation.

I find that by properly controlling the inward limit positions of the jaws 24 and the intensity of pressure applied thereto, root sections 14 of satisfactorily uniform cross sectional dimensions and configuration can be reproduced in quantity so as to snugly fit a series of hub sockets 10 of uniform dimensions and configuration. Such fitting may be of suflicient accuracy to position all of the abrasive segments A with their outer ends disposed uniformly on a cylindrical periphery constituting the working periphery of the rotary abrasive drum. It will be understood that it is necessary that such uniform radial positioning be attained in order that the drum may be properly balanced for high speed rotation, sufiiciently free from vibration resulting from lack of dynamic balance to provide for smooth operation against a work surface. Furthermore, the hardening of the root section 14 and the maximum density which is imparted to the narrowed waist section thereof, provides maximum strength and rigidity in the root section such as to support the freely flexible working portions 15 of the abrasive sheets for maximum efiiciency of abrasive action. Tilting of the segments circumferentially with reference to their sockets 10 is prevented. The root ends of the free working portions 15 of the leaves are stifily held in respective radial planes, and circumferential bending of the leaves arises wholely from the flexible bowing of the free working portions of the leaves. Thus a 4 desirable median between stiifness and flexibility is attained, and the degree of flexibility is regulated wholely by the radial length of the free working portions 15 of the sheets.

Modified F0rmFIG. 6

FIG. 6 illustrates a modified form of abrasive segment with a fish-tail root section 14b, and shows a modification of the method, involving the application of adhesive at 20b to the spread apart upper ends of a series of abrasive sheets 12, by ejecting the adhesive from a nozzle 23. In this case, the root portions of the abrasive sheets 12 and spacers 16b are fanned apart at their ends by applying pressure thereto along a line spaced from the ends of the sheets, using a suitable pair of pressure jaws 24 in opposed relation. The ends of the abrasive sheets are maintained in the spread condition until the adhesive or resin 2912 has hardened or cured so as to bond the other areas of the abrasive sheets together in a hard, rigid sandwich structure, with a fish-tail root section 1412.

FIG. 6 also illustrates the possibility of utilizing spacers of the same area as the abrasive sheets 12, the free areas of the spacers functioning to protect the back surfaces of the abrasive sheets from abrasive action by the abrasive coatings on adjacent sheets.

In FIGS. 4 and 5, the root sections 14 are composed of the bent root portions of abrasive sheets 12 and intervening bonding layers consisting in the separator strips 6 and the body of resin or adhesive impregnating the same, said interventing bonding layers being of double thin, wedge shape so as to collectively impart the doublewedge cross section of the composite sandwich structure constituting the root section 14 of the segment. Similarly, in FIG. 6, the root section 14b comprises the fanned-apart root portions of abrasive sheets 12 and spacers 16b and a series of intervening bonding layers of thin Wedge form, consisting in bodies of hardened resin or adhesive filling the spaces between the fanned out ends of the sheets 12.

Modified F0rmFIG. 8

FIG. 8 illustrates a further modification of the abrasive pack wherein the butt 18a of the pack is composed of alternating series of root portions of abrasive leaves 12 and wedge-shaped spacers 16c, and wherein a thinned waist section is formed by bringing together the adjacent portions of leaves 12 where they project from the narrower margins of spacers 16c, and securing them by adhesive which may fill the spaces between the converging portions of sheets 12 adjacent the spacers 16, in the form of thin wedges 20c of cured adhesive, thus providing rigid, substantially incompressible sloping shoulders 27 for keying the butt into a retainer channel of a hub. The adhesive Wedges 20c extend between the contacting portions of sheets 12 at waist 17c to provide adhesive bonds in the waist area, but terminate there so as to leave the working areas 15 of the sheets free to flex from the waist 17c. Films of the adhesive are also interposed between the spacers and the leaves 12, securing them together to provide a solid butt section.

In each of its several forms, the invention provides a relatively thick butt section at the inner end of a pack of abrasive leaves, joined by a relatively thin waist section to the freely flexible working portions of the leaves, the word relatively being used herein in the sense that the butt section is thick relative to the Waist section, and the waist section is thin relative to the butt section.

FIG. 9 illustrates a further modification of the invention wherein the use of spacers is dispensed with and the root section 14 consists in the root portions of the abrasive leaves, in substantially faceto-back laminar assembly, with layers of adhesive 20d interposed between them,

filling the interstices between abrasive grains, and firmly uniting them in a root section which is composed of a butt portion 18d of uncompressed layers and a reducedthickness waist section 17d, wherein the abrasive grains of respective leaves are embedded in the back surfaces of adjoining leaves. Such embedment is attained by compressing the pack of leaves under high pressure between forming jaws 24d after the root area of the assembled pack of leaves has been impregnated with liquid resin; and then curing the resin to develop a hard, rigid root section 14d before releasing the pack from the jaws.

FIG. 7 shows a novel and improved rotary abrasive tool embodying a pair of my improved abrasive packs A mounted in diametrically opposed relation in dovetail socket heads lite on respective spokes 29 joined at their inner ends to a common hub 28 to constitute a rotor B. Heads 10a, and, consequently the tips of abrasive packs A, are disposed at uniform radial spacing from the axis of rotation of an arbor on which hub 28 is mounted, for rotating the tool. Packs A are mounted with their abrasive faces oriented on opposite sides of the rotor B, thus facing in a common direction circumferentially (with respect to the direction of rotation). Since the tool is substantially balanced dynamically, the tips of packs A may be caused to sweep the work surface with balanced contact, and a rapid and improved abrasive action is thereby attained.

I claim:

1. An abrasive pack comprising a plurality of abrasive leaves and at least one spacer interposed between them, said leaves and spacer extending continuously throughout the width of said pack, said spacer being of compressible material, secured to the root portions of said leaves, and compressed at a distance from the root end of the pack, so as to provide a thinned waist and a thicker butt of elongated form, extending full width of the pack for keying reception in an axially extending peripheral mounting socket of a rotary holder.

2. An abrasive pack comprising a plurality of abrasivecoated leaves having working portions in freely flexible association with one another; an elongated relatively thick butt section for keying reception in an axially extending peripheral mounting socket of a rotary holder; and a relatively thin waist section joining said working portions to said butt section; said butt section comprising a sandwich structure extending full width of the pack and composed of integral root portions of said abrasive leava and at least one spacer interposed between said root portions and bonded thereto, said spacer being of porous fibrous sheet material in the form of a strip extending lengthwise of said butt section, with its opposite faces bonded to adjoining faces of said root portions, and being impregnated with bonding adhesive material.

3. An abrasive pack as defined in claim 2, wherein said spacer is relatively narrow, with its longitudinal axis extending transversely of the pack parallel to the inner end thereof, and is compressed and thereby thinned along said longitudinal axis to provide said thin waist section of the pack, and said working portions extend beyond said spacer in spaced relation to one another.

4. An abrasive pack as defined in claim 2, wherein said waist section is located beyond said spacer and comprises portions of said leaves adjacent said spacer, bent toward one another and bonded directly to one another.

5. An abrasive pack as defined in claim 2, wherein said spacer is substantially coextensive with said leaves in area, and has a root portion thereof compressed and thereby thinned along an axis parallel to the root end of said pack, to provide said thin waist section.

6. A rotary abrasive drum, comprising: a rotary hub having a plurality of circumferentially spaced peripheral sockets extending parallel to its axis of rotation; and a plurality of abrasive segments each comprising a pack of 6 abrasive-coated sheets having working portions in freely flexible face to back association with one another, an elongated relatively thick butt section receivable in a respective socket of said rotary hub, to provide an anchoring connection such as to securely anchor the segment against radially outward displacement during rotation against a work surface, and a relatively thin waist section joining said working portions to said butt section; said butt section comprising a sandwich structure composed of integral root portions of said abrasive leaves and intervening solid adhesive bonding layers of wedge shape, said butt section being solid, dense and hard so as to provide said secure anchoring connection.

7. An abrasive drum as defined in claim 6, wherein said adhesive bonding layers are composed of spacer strips of porous material impregnated with hardened adhesive and compacted in their thinner areas to form said thin Waist section of the segment.

8. An abrasive drum as defined in claim 7, wherein said spacer strips are of maximum thickness where said root section is joined to the base areas of the freely flexible portions of said abrasive coated sheets, whereby the latter are slightly spaced apart for maximum freedom of flexing action.

9. An abrasive drum as defined in claim 6, wherein said adhesive bonding layers consist in solidified bodies of adhesive filling wedge shaped spaces between the root portions of said abrasive coated leaves and bonded thereto.

10. An abrasive segment for a rotary abrasive drum having in its periphery a holding socket extending parallel to its axis of rotation, comprising: a pack of abrasivecoated sheets having a width corresponding to the length of said socket and including working portions in freely flexible face to back association with one another, a relatively thick butt section of dove-tail cross section extending full width along the inner margin of said pack, receivable in and fitted to said holding socket so as to provide an anchoring connection such as to securely anchor the segment against radially outward displacement during rotation against a work surface, and a relatively thin waist section joining said working portions to said butt section; said butt section comprising a sandwich structure composed of integral root portions of said abrasive leaves and intervening solid adhesive bonding layers of Wedge shape, said butt section being solid, dense and hard so as to provide said secure anchoring connection.

11. A rotary abrasive drum, comprising: a plurality of abrasive segments each including a pack of flexible sheets having coatings of abrasive grains adhesively secured to forward faces thereof and having back faces in slightly spaced, generally parallel relation to the forward faces of adjacent sheets, each pack having a root section of wedge shape of maximum thickness at the inner end margin of the segment and a rotary hub having a plurality of circumferentially spaced sockets of corresponding cross section receiving the respective root sections to provide an anchoring connection such as to securely anchor the segments against radially outward displacement during rotation against a work surface, said root section comprising a solid, dense, hard sandwich structure composed of integral root portions of said abrasive leaves and intervening adhesive bonding layers securely joining said root portions to one another, said sandwich structure being compacted and densified along a line parallel to the inner margin of said root section so as to provide said wedge shaped cross section.

12. A method of fabricating an abrasive segment comprising a plurality of abrasive coated leaves including slightly spaced, generally parallel, freely flexible working portions and root portions which are adhesively joined in a solid, dense, hard, rigid sandwich structure of elongated wedge shape for mounting in an anchoring socket in a rotatable hub, comprising the following steps: assembling a plurality of said abrasive leaves with a series of intervening spacer strips between said root portions; impregnating the sandwich assembly of spacer strips and root portions of the abrasive leaves, with a liquid adhesive; and hardening said adhesive While applying compression to said sandwich assembly between a pair of parallel, elongated jaws, to form a thinned transverse elongated waist section therein.

13. A method of fabricating an abrasive segment comprising a plurality of abrasive coated leaves including slightly spaced, generally parallel, freely flexible Working portions and root portions which are adhesively joined in a solid, dense, hard, rigid sandwich structure of elongated Wedge shape for mounting in an anchoring socket in a rotatable hub, comprising the following steps: assembling a plurality of said abrasive leaves with a series of intervening spacer strips between said root portions; and with the freely flexible portions of the leaves projecting from the said spacer strips; applying adhesive between said leaves along a straight line adjacent and parallel to the margins of the spacer strips; and hardening said adhesive while compressing the leves together along said straight line to form a thin transverse waist section along the margins of said spacers, and a thicker butt section, comprising a sandwich structure of said spacers and root portions of the leaves adhesively secured together to provide a solid butt section for keying into a hub socket.

14. An abrasive segment for a rotary abrasive drum, comprising: a pack of abrasive-coated sheets having working portions in freely flexible face to back association with one another; a relatively thick elongated butt section of dove-tail cross section, receivable in a holding socket in a rotary hub, to provide an anchoring connection such as to securely anchor the segment against radially outward displacement during rotation against a work surface; and a relatively thin Waist section joining said working portions to said butt section; said butt section comprising a sandwich structure composed of integral root portions of said abrasive leaves and intervening solid adhesive bonding layers; and a waist sectionof less thickness than said butt section, integrally joining the latter to said working portions, said waist section consisting in parts of said root portions and intervening bonding layers wherein the abrasive grains of said root portions are embedded into the backs of adjoining root portions and held in such embedded condition by said bonding layers.

15. A rotary abrasive device comprising a pair of packs of abrasively-coated leaves having Working portions in freely flexible association with one another; a relatively thick butt section for keying reception in a mounting socket of a holder; and a relatively thin waist section joining said working portions to said butt section; said butt section comprising a sandwich structure composed of integral root portions of said abrasive leaves and intervening adhesive bonds joining said root portions to one another; and a rotor comprising a hub, a pair of spokes rigidly attached to and projecting diametrically from said hub, and a pair of socket heads on the outer ends of the respective spokes, having respective key-hole sockets fitted to and receiving said butt sections for keying the packs to the rotor.

16. A rotary abrasive device comprising a pair of packs of abrasive-coated leaves having working portions in freely flexible association with one another; a relatively thick butt section for keyin'g reception in a mounting socket of a holder; and a relatively thin waist section joining said Working portions to said butt section; said butt section comprising a sandwich structure composed of integral root portions of said abrasive leaves and intervening adhesive bonds joining said root portions to one another; and a rotor comprising a hub and a plurality of circumferentially spaced peripheral keyhole sockets extending parallel to the axis of rotation of said hub, said sockets being fitted to and receiving said butt sections for keying the packs to the rotor.

References Cited in the file of this patent UNITED STATES PATENTS Re. 24,143 Leggett Apr. 17, 1956 FOREIGN PATENTS 916,876 France Dec. 18, 1946 

